1. Field of the Invention
The present invention relates to a consecutive image processing system, more particularly, it relates to an improvement of moving images in the consecutive image processing system.
2. Description of the Related Art
Recently, with the greater development of digital techniques, especially of the Very Large Semiconductor Integration (VLSI) technique, many digital processing systems are widely employed in the field of broadcasting. As a result, it is possible to store, process and transmit the moving images at a high speed and with a superior quality and stability, compared with an analog processing method.
In the case of television (TV) broadcasting, the TV image is, in general, transmitted at thirty frames per second so that clear stable moving images can be obtained on a dislay device at the receiving side. In this case, however, it is difficult to rewrite the image data stored in all memory cells of each image memory at the desired transmission speed of the TV image, i.e., transmission speed of thirty frames per second (this phenomenon is called "real time processing").
Accordingly, a "loop-movie" technique, one type of consecutive image processing, has been developed to solve the above problem. In the "loop-movie" technique, the number of picture elements per frame is set to as low a number as possible, digital data corresponding to each frame is transmitted with a corresponding small number of bits, and thus the digital data is consecutively stored in the memories. Following these steps, the data is enlarged and displayed as consecutive images on the display device.
In general, there are many image processing procedures in the known digital image processing method, i.e., gradation processing, correction, space filtering processing, image moving, border extraction, and transmission band compression.
In TV broadcasting, the real time processing of moving images is performed by utilizing redundant space in the TV signal and by compressing the transmission band. Conventionally, many algorithms of the transmission band compression have been proposed, and there are two main methods of transmission band compression, i.e., an inner frame method and a frame interval method. The former method compresses the numbers of bit per one picture element in the TV image frame, and the latter method compresses the distance between adjacent frames by utilizing a high coefficient of correlation.
Other special effects besides the "loop-movie" technique are known in the digital image processing method, i.e., a freeze-frame effect, reduction effect, and enlargement effect. The freeze-frame effect is used for temporarily freezing (stopping) the moving images by utilizing the function whereby each moving image frame is stored in the form of digital information. The reduction effect is used for inlaying the image to an optional position on the display device, after reducing the image size. The enlargement effect is used for enlarging the image and displaying the enlarged image on the display device, after the image photographed by a camera has been reduced and transmitted to the display device.
Although it is difficult to perform the above various effects by an analog or optical processing method, it is easily possible to achieve the above effects by a digital processing technique. That is, these special effects can be performed by controlling the read/write addresses to a random access memory (RAM). The control of the read/write addresses is performed by a host computer.
In the consecutive image processing system utilizing the "loop-movie" technique as one of the above special effects, this technique is used, for example, for a weather forecast display in TV broadcasting. That is, during the weather forecast, changes of cloud position transmitted from a weather satellite are continuously displayed on a predetermined map. These position-change images can be performed by the "loop-movie" technique.
Conventionally, in the above case, definite image frames are compressed and transmitted from the image memory in the image control apparatus connected to the host computer to the display memories in the image display apparatus, and the transferred image is enlarged and displayed on the display device in the image display apparatus. That is, in the conventional technique, the contents of the image memory in the image control apparatus are transferred to the display memory in the image display apparatus and enlarged and displayed on the display device by corresponding them to a memory size of 1 to 1.
The various conventional techniques and the problems thereof will be explained in more detail hereinafter.